This invention relates to a process for the preparation of 8-methoxy-4,8-dimethyl-1-(4-isopropylphenyl)-nonane, a compound which is used as an insecticide for the purpose of controlling fire ants.
Fire ants are a nuisance to farmers, particularly in the Southern states, because they build mounds in fields, which makes it difficult to cultivate crops. In addition, machinery or equipment passing over the mounds is subject to damage. They also attack livestock and people in the field which they come into contact with. Fire ants are so named because when they bite there is a painful fire-like sting associated with the bite.
The compound 8-methoxy-4,8-dimethyl-1-(4-isopropylphenyl)nonane is patented by the U.S. Government under U.S. Pat. No. 4,002,769 and is disclosed to be useful in the control of flies and mosquitoes. As disclosed in the patent, this compound has been made by reacting para-isopropylbenzyl chloride with triphenylphosphine in the presence of an acetonitrile solvent to form paraisopropylbenzyl triphenylphosphonium chloride. The latter compound is in turn reacted with sodium methoxide followed by methoxycitronellal to produce the intermediate cis- and trans-8-methoxy-4,8-dimethyl-1-(4-isopropylphenyl)1-nonene, and this compound, in turn, is hydrogenated to form the end product.
The intermediate compound, sometimes referred to herein as dehydro MV-678, has the formula ##STR1##
The end product, sometimes referred to as MV-678, has the formula ##STR2##
Toluene has also been used as a solvent in the process for the production of the intermediate.
A specific problem which occurs in the process for making 8-methoxy-4,8-dimethyl-1-(4-ispropylphenyl)-nonane lies in the fact that at the end of the step involving the reaction of para-ispropylbenzyl chloride with triphenylphosphine, a solid is formed in the solution, that solid being para-isopropylbenzyl triphenylphosphonium chloride, and this solid is difficult and expensive to treat because it must be isolated and purified from the reactants, before the next step of the process.
This invention is thus concerned with a new and more economical process for the preparation of 8-methoxy-4,8-dimethyl-1-(4-isopropylphenyl)-nonane wherein the solid intermediate remains in solution or in a slurry without the need for isolation and purification, and the entire reaction is conducted in a liquid medium until such time as the end product is formed.